Breeding potato cultivars with tubers resistant to Phytophthora infestans

Available information has been reviewed on tuber resistance to P. infestans , its inheritance and breeding procedures used to obtain potato cultivars s uperior in this character. P. infestans is worldwide the most destructive potato pathogen. Tuber resis tance is an essential component of potato resistance as this pathogen is of ten responsible for tuber rot in storage, and infected tubers of susceptibl e cultivars provide an important way for its overwintering. In Europe many cultivars and advanced breeders selections have been obtaine d with tuber resistance to P. infestans, but in the last decades no progres s is noted in the mean level of this resistance in cultivars. The expressio n of tuber resistance depends to a large extent on testing conditions and t herefore it can be difficult to evaluate. Consequently making progress in b reeding is not easy, and also cultivar assessment data from various countri es sometimes differ considerably. It is concluded from published data that it should be easier to make progre ss in breeding potato cultivars with resistant tubers if more attention is paid to combining the various types of resistance which are already known, and if the genetic determination of durable resistance to P. infestans is b etter understood.